Spectrum Computing

Update two years later: It is fixed! I replaced all caps, but that did'nt fix my problem. But finally I got my hands on another zx spectrum. That one does not work. Probably RAM issue. I tried the ULA from that unit in my zx spectrum, and now I have a clear image! Hurray! So it was the ULA all this ...

If it really is a similar problem, I would love to know whether the ULA replacement fixed it or not. In the mean time I socketed IC3 & IC4. Swapped them, with no difference. Now started on replacing all ceramic capacitors. Which all measured way higher values than expected. (or is that normal? 7...

Oh no, my poor ULA. I hope she's ok. I'll try the IC3 & IC4 replacements first. Have to order them and will share my results. Will take a few days. Worst case, my ULA is gone, but I still had fun repairing and analysing, and I learned a lot. Thank you for all the help and instructions for now! R...

Ah thanks, that means all is allright. It confused me a lot, because all the pinouts I could find were as you described. That leaves me with these things I can try: Swap out lower RAM for known working ones Test my ULA in a known working machine At the moment I don't have a working spectrum and don'...

Thanks for the details instructions. Here are my (strange) results: (edit: colors and photo's addes) ULA Pin 13 reads 3.3 V (guess that's within the limits) Replaced the capacitor anyway. The old one measured 70 nF (out of circuit) which is not 47 nF that it should be. Still 3.3V though, which is to...

Well, swapping the 4116's did't do anything. In any configuration I still have the same problems on screen. The same unreadable characters in the same rows and columns.

What can I do to test the other possible cause you mentioned? With the IC3 and/or IC4?

Thanks for the quick response.
Good idea swapping the 4116's. I'll try that first in different configurations. And will come back to share the results.

I sure hope it's not the ULA though.

Hi, New member here. I have a ZX Spectrum 48K issue 3. Which was in a bad condition when I got it. With the help of internet and this forum I got to a point that it's almost working correctly, but I still have some problems. This is my first ZX Spectrum, but have done all sorts of repairs on other r...